1. Technical Field
The present invention relates to a semiconductor device that is capable of transmitting electric signals between two circuits to which electric signals having different potentials from each other are input.
2. Related Art
To transmit electric signals between two circuits to which electric signals having different potentials from each other are input, photo couplers are often used. Each photo coupler includes a light emitting element such as a light emitting diode and a light receiving element such as a photo transistor. The light emitting element converts an input electric signal into light, and the light receiving element returns the light to an electric signal. In this manner, photo couplers transmit electric signals to each other.
However, it is difficult to reduce the size of each photo coupler due to the light emitting element and the light receiving element. Also, where the frequency of electric signals is high, the electric signals cannot be followed. To counter these problems, there has been a technique for transmitting electric signals by inductively coupling two inductors, as disclosed in Japanese translation of PCT international application NO. 2001-513276, for example.
A structure in which a pair of inductors are used when a first semiconductor chip on the transmission side and a second semiconductor chip on the reception side are connected to each other through a transmission path is disclosed in Japanese Laid-open patent publication No. 2008-113093. More specifically, a transmission line and the first semiconductor chip are connected in a noncontact manner by electromagnetically coupling the pair of inductors on the transmission side. The transmission line and the second semiconductor chip are connected in noncontact manner by electromagnetically coupling the pair of inductors on the reception side.
Where the signal voltages of the transmission-side circuit and the reception-side circuit differ from each other, the distance between the two inductors forming a pair becomes shorter, if the transmission-side circuit and the reception-side circuit are connected with the pair of inductors. As a result, insulation between the transmission-side circuit and the reception-side circuit cannot be secured.